/Engine/Source/Runtime/Slate/Public/Framework/Application/SlateApplication.h
Gets whether or not a particular widget has any users focus, and if so the type of focus (first one found).
The optional will be set with the focus cause, if unset this widget doesn't have focus.
virtual [TOptional](API\Runtime\Core\IO\TOptional)< EFocusCause > HasAnyUserFocus ( const [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< const [SWidget](API\Runtime\SlateCore\Widgets\SWidget) > Widget ) const